Electrical regulation



1937- w. J. McLACHLAN ELECTRICAL REGULATION Filed July 24, 1936 5 Fig. I.

stance 2 a rm e n O n m ta r m /w M Y im w a u ymr W P H m MW 1 t Z w m I l /I 8 m 8 um. m M r mm m H P w Wm w m f. c r k K d m n m r L L U IIII ll 0 A x 2 m U Go a H mm m WM w m m P w P m\ w u\ Mm M (MM m 7 M Patented Aug. 31, 1937* 2,091,870

UNITED STATES PATENT (m rror-1- ELECTRICAL REGULATION Willard J. McLachlan, Scotia, N. Y., assignor to General Electric Company, a corporation of New York Application July 24, 1936, Serial No. 92,380 4 Claims (Cl. 171-119) My invention relates to electrical regulation the following description taken in connection with and more particularly to improvements in autothe accompanying drawing and its scope will be matic voltage regulation of medium voltage netpointed out in the appended claims.

work type alternating current electrical distribu- In the drawing, Fig. 1 is a diagrammatic showtion systems. ing of a system embodying'my invention and Fig. 5

Patent No. 2,046,990 issued July '7, 1936, on an 2 is a vector diagram for explaining its operation. application of Charles A. Woodrow and assigned Referring now to the drawing and more part0 the assignee of the present application relates ticularly to Fig. l, the circuit diifers from that of to an automatic current compensated voltage regthe Woodrow patent by the addition of capacitors 1U ulating arrangement for network type alternating I. These capacitors are connected in shunt to a current distribution systems which automatically network of conductors 2 having a high ratio of tends to raise the network voltage in response to resistance to reactance. Each of these conducnormal relatively high power factor lagging load tors 2 may be isolated from the others by means current in the network feeder circuits and which of circuit breakers 3 controlled by well known 1 tends to lower the voltagein response to relatively fault-responsive protective relay means (not low power factor lagging current circulating in shown) forming no part of this invention. This the parallel feeders. The raising action is to network is energized by feeder circuits 4 concompensate for the normal voltage drop in the nected to a high voltage bus 5 which is fed by one feeders and the lowering action is to eliminate or more generators 6. The bus voltage is stepped circulating current in the feeders. Circulating down to the regulated network voltage by means 20 current is caused by unequal feeder voltages and of typical automatic transformer voltage reguis lagging in the high voltage feeder. lators I. These regulators are provided with line I have found that when such an arrangement drop compensators having conventional resistis used with some medium voltage networks that ance elements but having negative reactance elethere is not proper discrimination between load ments which may be either a reversed inductive 25 and circulating current. Upon investigation I reactance element 8 or a capacitive reactance found that the reason for this is due to the rela element 9. With relatively high power factor tlvely high ratio of resistance to reactance of the current flowing through the feeder circuits the conductors of such networks. This high ratio so resistance elements operate in the usual manner raises the power factor of the circulating current to bias the regulators so as to cause them to raise 30 that it does not lag suiiiciently behind the normal the voltage and compensate for the voltage drop lagging load current. in the feeders. The reactance elements are rela- In accordance with my invention I solved the tively insensitive to relatively high power factor above problem by connecting one or more shunt currents. However, for relatively low power faccapacitors (static electrical condensers) to the tor currents the resistance elements are relatively 35 network. The very low power factor leading curinsensitive and the negative reactance elements rent drawn by these capacitors combines with the act to cause the regulators to lower the voltage lagging load current to produce a resultant curwhen the low power factor current is lagging. rent of relatively high power factor but, due to This lowering action acts as an effective means the shunt as opposed to a series connection of the for eliminating circulating currents which tend 40 capacitors, the capacitor current does not comto flow in a loop circuit comprising two feeders blue with the circulating current. The result is and the sections of the network and the bus that the difference in power factor between the between these feeders whenever the voltages of circulating current and the load current is inthe regulating transformers of the feeders are 46 creased enough to insure proper discriminatory unequal. action by the regulating means. I As the circulating current does not do any An object of my invention is to provide a new useful work it is of relatively low power factor and improved regulated electrical distribution and will be lagging with respect to the feeder system, circuit whose regulating transformer is at the 60 Another object of my invention is to provide higher voltage and will be leading with respect 50 an improved voltage regulating system for netto the feeder voltage whose regulating transwork distribution systems which discriminates former is at the lower voltage. The higher the properly between load current and circulating resistance of the network conductors relative to current. their reactance the higher the power factor of My invention will be better understood from the circulating current. 55

The operation of my invention can best be understood by reference to the vector diagram in Fig. 2. In this diagram the horizontal vector represents the voltage of the network. The low power factor current lagging this voltage by the largest angle represents the circulating current in a feeder circuit the voltage of whose regulating transformer is higher than it should be. The next most lagging current vector represents the normal load current in that feeder. When the capacitor current, which is represented by the vertical vector, is added to the normal load current the phase angle of the combined capacitor and load current is relatively small and the power factor of this combined current is very high. As shown in the diagram, the addition of the capacitor current to the load current substantially doubles the angle between the circulating current and the normal current in the feeder. By varying the size of the capacitor this angle may be made almost any desired value. Consequently the regulating apparatus can now very easily discriminate between the circulating current and the normal current in the feeders. I

The addition of the shunt capacitors also produces the following advantages. The normal feeder power factor is improved, the normal voltage drop in the feeders is reduced, the current demand on the generators is decreased and the system losses are decreased.

In actual practice it is desirable to be able to disconnect a feeder from the network. The boxes ill represent feeder circuit breakers provided for this purpose. I

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications can be made therein and I aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In combination, an alternating current dis-.

tribution system including a plurality of electrically parallel feeder circuits, automatic voltage regulating means for each of said feeder circuits, separate current responsive compensating means for causing each of said regulating means to lower the voltage in response to relatively low power factor lagging current and to raise the voltage in response to relatively high power factor lagging current, and means for increasing the phase angle between normal currents and abnormal circulating currents in said feeder circuit.

2. In combination, an alternating current distribution system including a plurality of electrically parallel feeder circuits, automatic voltage regulating means for each of said feeder circuits including line drop compensators having reverse reactance compensating elements, and an electrical condenser connected to said system so as to increase the phase angle between normal currents and abnormal circulating currents in said feeder circuit.

3. In combination, an electrical distribution network, a plurality of alternating current feeder 'circuits for said network, variable ratio transformers in said feeder circuits, voltage responsive means for controlling the ratio of said transformers so as to maintain substantially constant voltage on said network, line drop compensators for said voltage responsive means including reverse reactance compensating elements, and a capacitor connected to said network so as to increase the phase angle between normal currents and abnormal circulating currents in said feeder circuit.

4. In combination, an alternating current distribution system including a plurality of parallel alternating current feeder circuits, separate automatic voltage regulating means for each of said circuits, separate line drop compensating means for each of said voltage regulating means, each of said line drop compensating means having a reverse reactance compensation element so that said regulating means will lower the voltage level when the feeder-currents are nearer 90 lagging than when they are in phase and raise the voltage level when the feeder currents are more nearly in phase than they are 90 lagging, said feeder circuit having a high ratio of resistance and reactance so that the current circulating therein as a result of a difference in voltage in said feeder circuits is relatively highin power factor, and means for increasing the phase angle between the circulating current in said feeder circuits and the normal load current in said feeder circuits comprising means for causing a leading current component of predetermined value to flow through said feeder circuit.

WILLARD J. MCLACHLAN. 

